MiniDiscs are a physical audio format developed by Sony originally as a replacement to the Compact Cassette format.

MiniDisc’s main competitor was the Philips Digital Compact Cassette. The two almost engaged in a format war, before DCC just died.
Interestingly, because Sony and Philips were initially cooperating on the development of a successor to the Compact Cassette, Sony and Philips ended up co-owning both formats.

Playing around with the MiniDiscs remind me of when I would create mixes on CD-Rs for my family’s car. After doing this enough, I even commandeered my parents’ old portable CD player. There are two main reasons I stopped doing this: Whenever I’d make a mistake, it would be stuck on there, and this would annoy me; the portable CD player broke. MiniDiscs brought me back to those fun times, with the advantage that I could re-write the discs if I made a mistake.

• MiniDisc Wiki
  • A pretty good resource for MiniDisc stuff. For more links, you can go through it before I bother to add any more links.